1. Field of the Invention
The invention relates to an electromagnetic actuator for the control valve of a fuel injector for internal combustion engines.
2. Background Art
A fuel injection pump and control valve assembly of well known design is disclosed in U.S. Pat. No. 6,238,190. It comprises an injector pump body with a high pressure pump chamber that communicates with an injection nozzle and a control valve chamber located between the pump chamber and an outlet port for an injector nozzle. A plunger located in the pump chamber is actuated by a camshaft driven mechanical driver, which effects a pumping stroke of the plunger for each engine cycle of a four stroke engine cycle, each cycle corresponding to two engine revolutions.
The control valve chamber of the known design is situated in transverse disposition with respect to the direction of travel of the plunger. It occupies substantial space within the cylinder body. A separate electromagnetic actuator secured to the pump body is under the control of an electronic engine controller. The actuator strokes the control valve to define fuel pressure pulses at the nozzle as the plunger is driven through its working stroke. The control valve, which is moved by the actuator between open and closed positions, has a rate shape position disposed between the open position of the valve and the closed position.
Co-pending patent application Ser. No. 10/208,587, entitled xe2x80x9cFuel Injector For Diesel Engines,xe2x80x9d filed by W. Scott Fischer, David Eickholt, and Mike Weston on Jul. 30, 2002 (Attorney Docket No. DDTC 0204 PUS), discloses an injector assembly for an internal combustion engine, wherein the control valve and valve actuator are formed as a module that is independent of the pump body and the nozzle assembly, the module, the plunger body and the nozzle assembly being arranged in linear, stacked relationship with an economy of space. Assembly procedure, during high volume manufacture of the injector, is substantially simplified. The co-pending application is assigned to the assignee of the present invention.
Because of the integration of the actuator and the control valve within an independent module, it becomes necessary to provide a connector mechanism for the electromagnetic actuator for the control valve that can be readily detached as a separate component. The actuator also must be designed to minimize the area occupied by the actuator within the module itself while accommodating a secure electrical connection for actuator coil windings as the module is assembled with the pump body and the nozzle assembly. In addition, the connector mechanism must seal between internal diesel fuel under low pressure and external engine oil under no pressure.
The electromagnetic actuator of the invention is adapted for use with a control module of the kind described in the co-pending patent application previously identified. The actuator for the control valve comprises a separate subassembly as an element of the control module. The control module itself, as well as the actuator, may be replaceable components of the overall injector assembly.
The electromagnetic actuator, which is a detachable component of the module, includes connector pins that pass through, and are electrically shielded from, the pump body. An electrical connector assembly is mounted on the body of the injector assembly and is connected to an engine wiring harness. The connector pins register with electrical connectors of the connector assembly.
The electromagnetic actuator makes provision for efficient winding of the actuator coils on a bobbin to define a stator assembly that makes it possible to reduce the length of the connector pins. The stator assembly is capable of precisely locating the connector pins relative to the centerline of the plunger of the injector assembly. The pins are located by the stator so that the required space for the stator core may be reduced to a minimum.
The control module includes a fuel pressure control valve. The electronic actuator has an armature connected to the fuel pressure control valve. The centerline of the control valve extends in the direction of movement of the armature.
The stator assembly, which is adjacent the armature, has a core, an electric coil bobbin, coil windings on the bobbin, and a bobbin extension radially disposed relative to the control valve.
Electrical connector pins are secured to the bobbin extension and are connected to the coil windings. The connector pins extend in the direction of the valve centerline.
An external connector assembly is secured to the body of the fuel pumping cylinder. The connector has electrical conductors that establish a connection to a wire harness for an engine controller. The pins register with the electrical conductors as the control module is assembled in place adjacent the fuel pumping chamber body.
The bobbin radially positions the connector pins to effect a connection with the electrical conductors. The bobbin extension is strategically positioned to effect a reduced connector pin length and to facilitate winding of the coil windings on the bobbin.
The bobbin extension, the wire leads for the bobbin coil windings, and the adjacent ends of the pins are over-molded with an insulating and reinforcing material.
The bobbin and the coil windings are assembled within the stator core. The stator core then is assembled within the control module. The bobbin radial extension is located in an opening in the stator core.